Not only does food and habitat determine movement for Mule Deer, their breeding cycles are of great importance. Their rut usually begins in the fall, determined by when the does begin their estrus cycle. The bucks become aggressive and compete each other for the does. Like whitetail, the mule deer does that do not breed return to the estrus period within a month. The total gestation time for deer is about 190+ days. Fawn are bone in the spring and stay with the mothers through the summer.